1. Field of the Invention
The present invention relates to devices for observing the interior contents of a vessel or process pipeline, and more particularly to a method and apparatus for cleaning a transparent viewing window provided in a wall of the vessel or pipeline
2. Description of the Related Art
In certain industries, production processes and testing are carried out inside sealed vessels. Various devices are used for direct or remote viewing of the interior of a pressure vessel, reaction vessel, process pipeline, or the like. A simple device for this purpose is a transparent viewing window provided in a wall of the vessel or pipeline. By looking through this window, an operator can observe liquid levels, color changes, and other visually determinable factors taking place within the vessel or pipe. Several of these viewing windows are disclosed, for example, in U.S. Pat. Nos. 2,744,487; 3,299,851; 3,837,226; 4,245,566; 4,809,862; 6,104,483; and 6,359,742. For certain industrial processes, it is desired to use instrumentation, such as imaging and measuring systems in conjunction with a viewing device to provide remote analysis of the process conditions. For example, U.S. Pat. No. 4,977,418 describes a camera viewing device that provides remote viewing of a vessel interior.
U.S. Pat. No. 6,771,366, which is incorporated by reference herein in its entirety, describes a flow cell device system that includes an optical flow cell that enables automatic visual analysis and inspection of fluids for various characteristics including particle size, shape, color, and count, among others. The system includes two viewing ports, each containing a transparent glass window to allow illumination and/or viewing of a fluid in an aperture defined between the two viewing ports.
A problem associated with viewing windows of the prior art is that an internal surface of the viewing window can become coated over or obscured by process constituents coming into contact with the viewing window. This situation can occur when internal fluids are highly viscous or stop flowing for any reason.
U.S. Pat. No. 6,782,184, which is incorporated by reference herein in its entirety, describes a spray ring device that provides for cleaning of an internal process window. The spray ring extends forward of the process surface of the glass in order to allow for cleaning fluid to be sprayed back onto the glass to provide a cleaning function.
The conventional spray ring configuration causes a pocket in the flow of product in front of the viewing window. In many processes, such a pocket will allow material to pool and stick to the window and obstruct the view through the window. The pocket may also prohibit the use of the flow cell in applications where the gap between the viewing window and the illuminating window is required to be quite small. For example, the viewing window and the illuminating window may be required in certain applications to be extremely close to one another to achieve sufficient light penetration for an acceptable image to be captured by a camera through the viewing window. In addition, the pocket in front of the window may cause eddy currents to be created such that the same fluid is trapped in front of the window for an extended period of time, which would cause erroneous analysis results.
Thus, a need exists for a spray ring that can be used to clean the windows in a flow cell having a flow path between two highly polished windows such that no crevices or pockets are created between the windows for particulates to build up in and the gap between the windows can be extremely small.